This invention relates to an indicator of operating conditions in an internal-combustion engine. More particularly, it is an apparatus for indicating one of a plurality of conditions of an internal combustion engine, such as an outboard marine engine, at a remote location by an electrical connection that comprises a single insulated conducting wire.
Internal-combustion engines typically require the circulation of oil under pressure to lubricate working parts, and are typically designed to operate at or under a maximum temperature. It is common to monitor the presence and circulation of oil for lubrication by monitoring oil pressure. Marine engines may be air-cooled, but are more typically cooled by circulating water. Any failure of that circulation rapidly causes an increase in the temperature of the engine. Either an increase in engine temperature or a decrease in oil pressure represents information that should be communicated to the operator of the engine who can then take action to prevent damage to the engine. When the operator is located at a distance from the engine, as when the engine is controlled from the front of the boat, a remote pilot house or the like, it is necessary to communicate information detected by sensors at the engine to the remote location.
One attempt at solving the problem described above has been disclosed in U.S. Pat. No. 4,019,489, entitled "Safety Apparatus for Engines." The '489 patent discloses a system that is responsive to water pressure, oil pressure, and engine temperature. Each of these variables is detected by a conventional sensor that is connected by its own insulated wire to an electronic circuit at a remote location in a pilot house or the like. The use of such separate wires requires a multiwire cable or the equivalent connecting the engine with the control area. This represents a disadvantage that is overcome by the present invention.